What is an IP address?
An IP address is the destination label of the internet. When you request a page, your request has to say where the reply should go — and that “where” is an IP address. Without one, data has nowhere to come back to.
The format
There are two versions in use.
IPv4 addresses look like 203.0.113.42: four numbers from 0 to 255. That design allows about 4.3 billion addresses, which seemed generous in 1981 and ran out in the 2010s.
IPv6 addresses look like 2001:db8:85a3::8a2e:370:7334: eight groups of hexadecimal digits, with runs of zeros collapsed to ::. The address space is large enough that exhaustion is not a practical concern.
Both are in service simultaneously. Most connections today can use either, and which one a given request uses depends on what both ends support.
Public and private addresses
Your router holds one public address, visible to the whole internet, assigned by your provider. Behind it, every device gets a private address — 192.168.x.x, 10.x.x.x or 172.16–31.x.x — that has meaning only inside your home.
The router translates between the two. This is why every device in a house appears to the outside world as one address, and why typing 192.168.1.1 opens your router’s own settings rather than a website.
Who hands them out
Addresses are not invented locally. IANA allocates large blocks to five regional registries — ARIN, RIPE NCC, APNIC, LACNIC and AFRINIC — which assign them to providers, which assign them to you. Those allocation records are public, which is how any site can tell which network an address belongs to.
What it reveals
From an address alone, a site learns the country reliably, the region usually, the city approximately, and the owning network precisely. It does not learn your name, your street or who was using the device — that link exists only at your provider, and is disclosed on legal process.
Frequently asked questions
Does every device have its own IP address?
Every device has one on its local network. Usually they share a single public address, which is the one the rest of the internet sees.
Does my IP address change?
Most home connections get a dynamic address that changes occasionally — after a router restart, a line fault, or on the provider's own schedule. Business lines often pay for a static one.
Is an IP address personal data?
Under the GDPR, yes. European courts have held that a public IP address is personal data for anyone who can link it to a subscriber, which is why sites that process it need a lawful basis.
Can two devices share one IP address?
Constantly. Every device behind your router shares its public address, and carrier-grade NAT puts thousands of subscribers behind a single one.